Masoneilan 96/97 Series Pneumatic Rack-and-Pinion Actuators

Overview

The Masoneilan 96/97 is a series of pneumatic rack-and-pinion actuators from Baker Hughes for automating quarter-turn valves. The 96 is the double-acting version, driven by air in both directions, and the 97 is the spring-return version, which adds spring cartridges so the valve moves to a safe position if the air supply is lost. The instruction manual for the series, Rev. A, estimates a useful life of more than 25 years when the actuator is installed correctly and inspected every year, which is a long service horizon for a compact pneumatic drive.

Seven Star LLC is the trusted supplier for Masoneilan in the Sultanate of Oman and supplies the Masoneilan 96/97 actuators with the butterfly, ball and plug valves they operate. Our Muscat engineers can help specify double-acting or spring-return action, fail-open or fail-closed orientation and the solenoid and filter arrangement, so that a plant in the GCC receives an actuator that suits the way its valves are piped and controlled.

Operating Principle of the Masoneilan 96/97

Inside the Masoneilan 96/97 body two pistons carry racks that engage a central pinion. In the 96 double-acting actuator, air entering Port A pushes the pistons apart and turns the pinion counter-clockwise, while air entering Port B is routed through an internal passage to the outer side of the pistons, forcing them together and turning the pinion clockwise. In normal assembly, the clockwise stroke closes the attached valve and the counter-clockwise stroke opens it.

In the 97 spring-return version, spring cartridges act on the pistons and push them together when air pressure is lost. That spring stroke normally closes the valve, so the standard 97 is fail-closed. The recommended operating medium is clean, dry industrial compressed air at 40 to 140 psig (3 to 10 bar), the maximum pressure rating of the actuator is 140 psig (10 barg), and the recommended temperature range is -20 degF to 200 degF (-29 degC to 95 degC).

Fail-Open and Fail-Closed Configurations of the Masoneilan 96/97

The manual describes three methods for converting a Masoneilan 96/97 spring-return actuator to fail-open. Method 1 turns the actuator so its long side is perpendicular to the pipeline, which reverses the spring direction and works only with concentric disc valves. Method 2 removes the end caps and pistons, rotates the pinion by 90 degrees and refits it, which keeps the actuator parallel to the pipeline and again suits concentric disc valves. Method 3 reverses the pistons so the racks turn the pinion the other way, and it works for all valves, including offset disc butterfly valves that may only turn clockwise to close.

These options matter during procurement because the choice depends on the valve, not only on the actuator. The manual also warns that a butterfly valve left with its disc open or closed by the actuator can be damaged during installation: an open disc exposes the sealing edge, and a disc closed for a long time can create a compression set on the seat. Scribing the valve and actuator before removal, so that the actuator returns to the same quadrant, is the practice Baker Hughes recommends.

Engineering Design of the Masoneilan 96/97

The Masoneilan 96/97 body is a rack-and-pinion assembly with the pinion supported by bearing rings and sealed with O-rings. A cam on the pinion gives the travel-stop function. Two travel stop screws with lock nuts are set at the factory for 90 degrees of travel, and the actuator is designed with a nominal 5 degrees of over or under travel at each end, with extended travel stops in the end caps available when more adjustment is needed. A position indicator pointer sits on the top of the pinion, and the top wrench flats allow the valve to be turned by hand during setup.

Mounting follows a simple pattern. The actuator mounts directly on the top plate of Masoneilan valves using the studs and nuts of a mounting kit, with the nuts torqued in a diagonal sequence to load the studs equally. The manual recommends lubricating the output bore with thick grease so the actuator can be removed from the valve stem even after years of service, and it specifies a lithium-based NLGI grade 2 extreme-pressure grease for assembly of the Masoneilan 96/97.

Key Features

The following points summarise what makes the Masoneilan 96/97 practical for valve automation:

• The Masoneilan 96/97 comes as a 96 double-acting actuator and a 97 spring-return actuator, so one body design serves both modulating and fail-safe duty.
• The double piston, rack and pinion mechanism turns the valve stem through a quarter turn of 90 degrees.
• Spring cartridges in the 97 return the valve to a safe position without air, normally fail-closed.
• Fail-open operation can be obtained by turning the actuator, rotating the pinion or reversing the pistons.
• The rated air pressure is 140 psig (10 barg) and the recommended operating temperature is -20 to 200 degF (-29 to 95 degC).
• Adjustable travel stops provide a nominal 5 degrees of over or under travel, with extended stops available on request.
• A 40 micron or finer filter, and a four-way solenoid that fills the spring chambers with clean air, are recommended to extend service life.
• The manual quotes an estimated useful life of 25 years or more under correct installation and annual inspection.

Industrial Applications

The Masoneilan 96/97 is used to open and close or throttle quarter-turn valves in utilities and process plants: cooling water and seawater butterfly valves at coastal plants near Sohar and Salalah, fire water isolation, desalination and water treatment headers, and chemical dosing lines. The fail-closed spring return of the 97 suits isolation duty, while the 96 suits applications where the valve should stay in position on air loss or where an external safety system provides the fail action.

In Oman and the GCC, Seven Star LLC supplies the Masoneilan 96/97 together with valves from the same range, such as the Masoneilan 37002 MiniTork II butterfly control valves and the Masoneilan 39005 high performance butterfly valve. Our team can compare rack-and-pinion drive with diaphragm and cylinder actuators and recommend the best fit for the torque, speed and fail-safe requirement.

Technical Specifications

The table summarises the data published for the Masoneilan 96/97 in the Baker Hughes instruction manual (Rev. A). The manual does not publish a torque table, so torque output must be confirmed with Baker Hughes for each actuator size.

Other Masoneilan actuators and positioners include the Masoneilan Type 37/38 pneumatic spring-diaphragm actuator and Masoneilan 8013 electro-pneumatic cam positioner.

Request a Quote for Masoneilan 96/97

To request pricing or technical support for the Masoneilan 96/97, send a formal RFQ to the Seven Star LLC instrumentation division with the valve type and size, the required torque, double-acting or spring-return action, the fail direction and the air supply conditions. We can check availability and lead time, advise on solenoid and filter arrangements and provide the Baker Hughes instruction manual from this page. In Oman and the GCC, Seven Star LLC supplies genuine actuators with manufacturer documentation and local engineering support.